CN116081620B

CN116081620B - A method for preparing desulfurization and denitrification activated carbon using coking wastewater concentrated brine

Info

Publication number: CN116081620B
Application number: CN202211563631.5A
Authority: CN
Inventors: 张慧荣; 罗琳; 牛健; 郭彦霞; 程芳琴
Original assignee: Shanxi University
Current assignee: Shanxi University
Priority date: 2022-12-07
Filing date: 2022-12-07
Publication date: 2025-01-28
Anticipated expiration: 2042-12-07
Also published as: CN116081620A

Abstract

A method for preparing desulfurization and denitrification active carbon by using coking wastewater strong brine belongs to the technical field of preparation and application of active carbon, and can solve the problems of higher cost, lower performance, higher treatment difficulty of coking wastewater strong brine and the like of the active carbon in the prior art. The method comprises the specific steps of S1, sampling coking wastewater strong brine, measuring the concentration of Na ⁺、Ca²⁺、Cl^‑、SO₄ ^2‑ in the coking wastewater strong brine, S2, crushing raw coal for preparing activated carbon to be more than 160 meshes, S3, mixing the coking wastewater strong brine with the raw coal according to a certain proportion, wherein the adding proportion of the coking wastewater strong brine is not more than 10% of that of a coal sample, and S4, adding a binder into the mixed sample, and then preparing the desulfurization and denitrification activated carbon through hot press molding, carbonization and CO ₂/steam activation. The invention strengthens the desulfurization and denitrification activity of the activated carbon by utilizing the strong brine of the coking wastewater, and is beneficial to promoting the reduction, recycling and reutilization in the coking industry.

Description

Method for preparing desulfurization and denitrification active carbon by using coking wastewater strong brine

Technical Field

The invention belongs to the technical field of preparation and application of active carbon, and particularly relates to a method for preparing desulfurization and denitrification active carbon by using strong brine of coking wastewater.

Background

Nitrogen oxides (NO _x) and sulfur oxides (SO _x) discharged in the coking production process can cause ecological environment problems such as acid rain, ozone layer cavities and the like. Meanwhile, china comes out of the strict ultra-low emission standard (NO _x＜50 mg•Nm^-3;SO_x＜35 mg•Nm^-3). However, because the coke oven flue gas has lower temperature (180 ℃) and complex flue gas components, the mature flue gas desulfurization and denitrification technology of the thermal power plant cannot be popularized to the coking industry. The integrated active carbon technology for simultaneously desulfurizing and denitrating has the advantages of simultaneously removing various pollutants, basically not consuming water, having no secondary pollution and the like, and is successfully applied to the field of low-temperature flue gas treatment of coke ovens and the like. But the relatively high cost and low performance of activated carbon prevent further popularization and application.

Meanwhile, a large amount of coking wastewater strong brine is discharged in the coking production process. The development and implementation of "zero discharge" of coking wastewater increases the operating cost of the coke-oven plant. The traditional wet quenching process can absorb part of the coking wastewater strong brine, but can cause the problems of coke strength reduction and the like, and along with the popularization of the dry quenching process, the coking wastewater strong brine is more treated by adopting a mode of concentrating before crystallizing. The method has the problems of high equipment loss rate, high operation cost, low resource recovery rate and the like. Patent ZL200610056702.7 discloses that impregnated activated carbon is prepared by impregnating Na ⁺ plasma on activated carbon and used for purification of SO ₂ and NO ₂. Patent CN115171798a discloses that Na in coal can promote the desulfurization and/or denitration activity of activated carbon. The coking wastewater strong brine contains a large amount of Na ⁺, so that the preparation of the activated carbon by using the coking wastewater strong brine can necessarily optimize the physical and chemical structure of the activated carbon and strengthen the desulfurization and denitrification activity, thereby reducing the production cost of the activated carbon.

Disclosure of Invention

Aiming at the problems of higher cost, lower performance, higher treatment difficulty of strong brine of coking wastewater and the like of the active carbon. The invention provides a method for preparing desulfurization and denitrification active carbon by using strong brine of coking wastewater. The method has the advantages of simple steps, easy operation, easy popularization and implementation in the coking industry, and the like, and is beneficial to realizing reduction, recycling and reutilization in the coking industry.

The invention adopts the following technical scheme:

a method for preparing desulfurization and denitrification active carbon by using coking wastewater strong brine comprises the following steps:

S1, sampling concentrated brine of the coking wastewater and measuring the concentration of Na ⁺、Ca²⁺、Cl^-、SO₄ ^2- in the concentrated brine;

S2, crushing raw coal prepared by activated carbon to more than 160 meshes;

S3, mixing strong brine of the coking wastewater with raw coal according to a proportion to obtain a mixed sample;

S4, adding the binder into the mixed sample, and then performing hot press molding, carbonization and CO ₂/steam activation to prepare the activated carbon.

Further, in the step S2, at least three groups of activated carbon preparation coal samples are taken.

Further, in the step S3, the concentration of Na ⁺ in the strong brine of the coking wastewater is generally 4-20 g/L, and excessive addition of Na ⁺ can cause collapse of the pore structure of the activated carbon due to excessive activation, and the adsorption performance is reduced, so that the addition proportion of the strong brine of the coking wastewater is not more than 10% of the mass of the raw coal.

Further, in the step S4, the binder comprises coal tar and/or asphalt, wherein the mass ratio of the mixed sample to the binder is 70-80:20-30, the hot press molding condition is that the pressure is 25-35 MPa, the temperature is 75 ℃, the carbonization temperature is 450-750 ℃, the carbonization time is 40-100 min, the activation temperature is 800-950 ℃ and the activation time is 20-60 min.

The beneficial effects of the invention are as follows:

The invention provides a method for preparing desulfurization and denitrification active carbon by using strong brine of coking wastewater, which has the advantages of simple steps, easy operation, easy popularization in coking industry and the like. The invention uses the strong brine of the coking wastewater to strengthen the desulfurization and denitrification activity of the activated carbon. The invention not only realizes the resource utilization of the strong brine of the coking wastewater, but also reduces the preparation cost of the activated carbon, and has remarkable promotion effect on the clean production and sustainable development of the coking industry.

Drawings

FIG. 1 is a graph showing the denitration rate change trend of AC-40-xCW at 120 ℃;

FIG. 2 is a graph showing the trend of sulfur capacity change at 120℃for AC-20-xCW.

Detailed Description

S2, crushing raw coal prepared by activated carbon to more than 160 meshes;

Example 1

The invention provides a method for preparing desulfurization and denitrification active carbon by using strong brine of coking wastewater, which specifically comprises the following steps:

1. uniformly mixing the coking wastewater strong brine with coal;

5wt.% of concentrated brine of coking wastewater is added to Fugu sub-bituminous coal of Shaanxi. Wherein the main ion concentration of the strong brine of the coking wastewater is shown in table 1:

TABLE 1 concentration of major ions in concentrated brine of coking wastewater

2. Preparing active carbon;

The preparation method of the activated carbon comprises the steps of adding 23wt.% of binder (a mixture of coal tar and asphalt, wherein the mass of the binder and the mixture of coal tar and asphalt is 3:2) into a mixed sample, uniformly mixing, performing hot press molding (constant temperature and pressure for 5min at 75 ℃ and 25 MPa), carbonizing at 600 ℃ for 1h to obtain a precursor, crushing the precursor to 20-40 meshes, and activating 10g of the precursor for 40min under the atmosphere of lower water vapor (water inflow: 0.06 mL/min.g and 900 ℃) to obtain the desulfurization and denitrification activated carbon named as AC-b-xCW, wherein b is the activation time, and x is the addition proportion of strong brine of coking wastewater.

3. And (5) testing performance.

The denitration performance of the prepared activated carbon is obtained through a simulated coke oven smoke composition test. The simulated flue gas composition was 5 Vol% O ₂,450 ppm NO,450 ppm NH₃,N₂ as balance gas, total gas flow 100 mL/min, airspeed 4000 h ^-1, and temperature 120 ℃. The denitration rate (Re) calculation formula is as follows:

Wherein C _in,C_out is the inlet and outlet concentration of NO, respectively.

TABLE 2 denitration rate Change of AC-40-xCW

Example 2

The preparation method of the activated carbon is basically the same as that of the embodiment 1, except that the adding proportion of the coking wastewater strong brine in the mixed sample is 8 wt percent, the mass of the precursor in the activation process is 7g, and the activation time is 20 min. The activated carbon prepared with or without adding the coking strong brine was named AC-20-8CW and AC-20-0CW, respectively. Desulfurization tests were performed in a simulated flue gas atmosphere of 6 Vol% O ₂, 10 Vol% steam, 1400 ppm SO ₂,N₂ as balance gas, total gas flow of 200 mL/min, space velocity of 6000 h ^-1, and temperature of 120 ℃. The saturated sulfur capacity (S) of activated carbon can be calculated by the following formula:

Wherein F is the simulated total flow of flue gas (mL/min), M is the mass of activated carbon (g), t _q is the stoichiometric time of adsorption, 60 min in this experiment, and C _in,C_out is the inlet and outlet concentrations of SO ₂, respectively.

TABLE 3 Sulfur capacity Change of AC-20-xCW

The principles and embodiments of the present invention have been described herein with reference to two examples, the above examples being provided only to facilitate an understanding of the core methods and core ideas of the present invention. While the foregoing is directed to the preferred embodiment of the present invention, it is pointed out that various modifications and variations of the invention will be apparent to those skilled in the art.

Any modification, equivalent replacement, improvement, etc. made or the inventive concept and technical solution without improvement directly used in other occasions should be regarded as the protection scope of the present invention.

Claims

1. A method for preparing desulfurization and denitrification activated carbon using coking wastewater concentrated brine, characterized in that it comprises the following steps:

Step a, pre-treating the coking wastewater brine and determining the ion content: mixing the coking wastewater brine containing Na ⁺ , Ca ²⁺ , Cl ^- , and SO ₄ ^2- ions with raw coal with a particle size of 160 mesh or more to obtain a mixed sample, wherein the addition ratio of the coking wastewater brine does not exceed 10% of the mass of the raw coal, and the Na ⁺ concentration in the coking wastewater brine is 4-20 g/L;

Step b, mixing the mixed sample with a binder in a mass ratio of 77:23, wherein the binder is a mixture of coal tar and asphalt in a mass ratio of 3:2, and hot pressing at a pressure of 25-35 MPa and a temperature of 75° C. for 5 minutes;

Step c, carbonizing the hot pressed coal sample at a temperature of 450-750° C. for 40-100 minutes;

Step d: The carbonized sample is crushed into 20-40 meshes, and activated with _CO2 or water vapor at a temperature of 800-950°C for 20-60 minutes to obtain desulfurization and denitrification activated carbon.